- Background Intradepartmental and interdepartmental benchmarking requires scoring systems with reliability (calibration) and stability over the complete spectrum of periprocedural risk. The aim of this single-center study was to assess the performance of the 2000 Bernstein-Parsonnet risk stratification model in cardiac surgery, by itself and against the EuroSCORE. Methods A prospective observational design was used. The study group consisted of 1,639 consecutive patients of mean age 64.6 ± 12.04 years who underwent elective or emergency cardiac surgery from January 2003 to June 2004. The probabilities of hospital death were estimated with the 2000 Bernstein-Parsonnet and EuroSCORE algorithms. The correlation of predicted and observed mortality was compared between the two models, and score validity was assessed by calculating the area under the receiver operating characteristic (ROC) curve. Results The patients were stratified into five risk groups according to their scores in the two models. For the 2000 Bernstein-Parsonnet model, findings were as follows: score 0–10: predicted mortality 0%–2.2%, observed mortality 0.6%; score 10.5–20: predicted 2.3%–4.7%, observed 2.3%; score 20.5–30: predicted 4.8%–10%, observed 6.7%; score 30.5–40: predicted 10.1%–23%, observed 11.5%; and score greater than 40: predicted 23.1%–80%, observed 29.9%. For the EuroSCORE, findings were as follows: score 0%–2%: predicted mortality 1.1%, observed mortality 0.6%; score 3%–5%: predicted 2.1%, observed 3.0%; score 6%–8%: predicted 4.1%, observed 3.5%; score 9–11: predicted 7.6%, observed 6.6.%; and score greater than 12: predicted 13.8%, observed 14.0%. There was good agreement between the observed and expected number of deaths, with both models. The area under the ROC curve was higher for the Bernstein-Parsonnet model (0.83, odds ratio [OR] 2.01, 95% confidence interval [CI] 1.75–2.31, p < 0.0001) than for the EuroSCORE (0.73, OR 1.05, 95% CI 1.04–1.07, p < 0.001). Conclusions The 2000 Bernstein-Parsonnet model is a simple, objective system for the estimation of hospital mortality in patients undergoing cardiac surgery, with slightly higher calibration and discrimination than the EuroSCORE additive model.